Remove use of deprecated base::ListValue::Append(Value*) overload in extensions.

extensions/browser/api/web_request/web_request_api_helpers.h

Index: extensions/browser/api/web_request/web_request_api_helpers.h
diff --git a/extensions/browser/api/web_request/web_request_api_helpers.h b/extensions/browser/api/web_request/web_request_api_helpers.h
index 450f3cae2f0a342e19b828f370609bcde56fe00c..a46ec376f88162fa82f39d7d8807fa47ff08c08b 100644
--- a/extensions/browser/api/web_request/web_request_api_helpers.h
+++ b/extensions/browser/api/web_request/web_request_api_helpers.h
@@ -342,9 +342,10 @@ void NotifyWebRequestAPIUsed(void* browser_context_id,
 void SendExtensionWebRequestStatusToHost(content::RenderProcessHost* host);
 
 // Converts the |name|, |value| pair of a http header to a HttpHeaders
-// dictionary. Ownership is passed to the caller.
-base::DictionaryValue* CreateHeaderDictionary(
-    const std::string& name, const std::string& value);
+// dictionary.
+std::unique_ptr<base::DictionaryValue> CreateHeaderDictionary(
+    const std::string& name,
+    const std::string& value);
 
 // Returns whether |type| is a ResourceType that is handled by the web request
 // API.